1. Field
The present invention relates to an integrated circuit, a self-test method for the integrated circuit, and an optical disc apparatus including the integrated circuit. In particular, the present invention relates to an integrated circuit including an AD converter, a self-test method for the integrated circuit, and an optical disc apparatus including the integrated circuit.
2. Description of the Related Art
Today, the frequency of reproduced signals from optical discs is being significantly increased by the emergence of high-density recording optical discs, such as HD DVDs. Accordingly, the conversion speed of an AD converter for sampling and converting reproduced signals to digital form is also being increased.
At the same time, to maintain the quality of reproduced signals at a high level, it is very important not only to ensure high conversion speed, but also to ensure high conversion performance (such as high linearity, low noise performance, or low distortion performance) of an AD converter.
Therefore, performance evaluations and quality assurance for an AD converter are very important issues that will affect performance evaluations and quality assurance for an optical disc apparatus.
Conventionally, there have been proposed various evaluation methods and apparatuses for evaluating the performance of AD converters. For example, JP-A 11-98016 discloses a technique relating to an evaluation apparatus which evaluates the performance of AD converters. In operation, this evaluation apparatus inputs a sine wave to an AD converter, temporarily stores digital data output from the AD converter in a waveform memory, reads the digital data from the waveform memory to perform signal processing for frequency transform (such as FFT or wavelet transform) on the digital data, and thus evaluates the performance of the AD converter.
For evaluating an AD converter, it is important not only to evaluate the individual performance of the AD converter, but also to evaluate the performance of the AD converter when it is included in an apparatus and operates in the operating environment of peripheral circuitry. In other words, it is necessary to provide the capability of performing self-testing and performance evaluations on the AD converter when it is included in the apparatus.
In response to demands for smaller and lower cost optical disc apparatuses, there have been developed configurations in which an AD converter and many other digital circuits are built in a single, highly integrated circuit. In such a configuration, it is technically difficult to externally extract the output of an AD converter alone at a high speed.
In this case, incorporating a self-test circuit into the highly integrated circuit, instead of extracting the output of the AD converter to the outside of the highly integrated circuit, is effective. However, the configuration disclosed in JP-A 11-98016 cannot be regarded as a reasonable solution in terms of cost and use efficiency of an integrated circuit, since the waveform memory and large circuitry involved in signal processing for frequency transform are included as part of a self-test circuit in the integrated circuit.